NOTE: This answer relates to a rule proposed by REC and does not reflect current regulations in effect:
For simplicity, we used the standard distance to the 80 dBu service F(50,50) contour for each FM service class as well as the three "tiers" of FM translator "sub-classes". If the distance from to all short-spaced second adjacent channel stations is less than the 80 dBu standard distance, then the waiver is considered "easy" and if there is at least one short-spaced station with a distance further than the 80 dBu standard distance, then the waiver is considered "hard". The stronger the short-spaced second-adjacent channel stations are, the easier it is for the LPFM station to protect the short-spaced station(s). Easy waivers can mean that rooftop antennas, smaller antennas and locations in more densely populated areas where hard waivers require increased height, larger antennas, more remote locations (reducing population coverage) and in some cases, contour overlap studies.
